This invention relates to magnetic recording disk drives, and more particularly to disk drives that prevent corrosion of the magnetic elements of the read/write heads.
Magnetic recording disk drives store digital data in the magnetic recording medium of a rotating storage disk. The disks are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at high speed. Data is stored as magnetic transitions on the disks in a plurality of concentric circular data tracks. The data is recorded and read by a read/write transducer or head. Each read/write head is located on the trailing end of an air-bearing slider, with the air-bearing surface (ABS) of the slider supporting the slider above the rotating disk. Each slider is mounted on the end of an arm of a rotary actuator that moves the sliders and attached heads across the disk surfaces. The write head is an inductive write head with the magnetic elements being the magnetic poles that generate the magnetic write fields. The read head is a magnetoresistive (MR) read head, which may be a spin-valve type giant magnetoresistance (GMR) sensing element, or the more recently proposed magnetic tunnel junction (MTJ) sensing element.
An important parameter affecting the recording density of a disk drive is the magnetic spacing between the magnetic elements (the write poles and the MR sensing element) and the magnetizable medium of the disk. Closer magnetic spacing allows for smaller magnetic xe2x80x9cbitsxe2x80x9d, which in turn allow for narrower track widths and consequently a greater recording density. However, the magnetic spacing is limited to a certain extent by the thickness of the protective overcoat on the magnetic elements, which is required because the magnetic elements are formed of materials that are highly corrosive, especially in the presence of water vapor. For example, the magnetic elements may typically contain materials such as Co, Ni, Fe, Ta, and Cu. More specifically, MR sensing elements, including MTJ sensing elements, may contain Co, Cu, Ru, NiO, FeMn and NiMn, and high-moment write poles may contain alloys of Co, Fe and Ni. These metallic head materials are susceptible to corrosion during manufacture, storage and use. The protective overcoat protecting the magnetic elements is typically a thin amorphous xe2x80x9cdiamond-likexe2x80x9d carbon overcoat. In the absence of this impermeable overcoat, water and other corrosive vapors are able to penetrate into the reactive metal films of the magnetic elements, thus rendering the read/write head unreliable.
A self-limiting wear contact pad (or xe2x80x9cprotrusion padxe2x80x9d) air-bearing slider provides for very low and tight tolerance magnetic spacing by reducing the effect of tolerances associated with slider fabrication and disk dive mechanical assembly, elimination of head overcoats, and elimination of head recession. This type of air-bearing slider, in which the head overcoat and part of the protrusion pad are relatively quickly xe2x80x9cburnishedxe2x80x9d or worn away during initial contact with the rotating disk, is described in IBM""s pending application xe2x80x9cSelf-Limiting Wear Contact Pad Slider and Method for Makingxe2x80x9d, Ser. No. 09/687,234 filed Oct. 13, 2000, which is incorporated herein by reference. However, the absence of a head overcoat to protect the magnetic elements has been discovered to be unacceptable in conventional disk drives due to the risk of corrosion. Thus disk drives with vapor phase corrosion inhibitors (VPCI) to prevent corrosion of uncoated heads has been proposed, as described in IBM""s pending application xe2x80x9cMagnetic Recording Device with Improved Reliabilityxe2x80x9d, Ser. No. 10/051,866 filed Jan. 15, 2002, which is incorporated herein by reference.
What is needed is a disk drive with a read/write head that does not require a protective coating to prevent corrosion of the head""s magnetic elements so that the magnetic spacing in the disk drive can be reduced.
The present invention is a disk drive with self-limiting wear contact type air-bearing sliders with overcoated heads to protect the magnetic elements during slider fabrication and disk drive assembly, but in which the overcoats are later removed and the heads maintained in a hermetically sealed disk drive housing. The overcoated protrusion pad sliders are assembled into the disk drive in a special environment, typically air with humidity controlled below a level above which corrosion of the magnetic elements would occur. The drive is then hermetically sealed and the drive is operated with the protrusion pads in contact with the disks until the overcoats and a portion of the pads are worn or burnished away. The combination of protrusion pad air bearing sliders with a hermetically sealed disk drive in a controlled atmosphere, and the burnishing of the head overcoat either after the drive has been sealed or under controlled humidity conditions prior to sealing, allows for a very low magnetic spacing to be achieved in manufacturable disk drives.
For a fuller understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken together with the accompanying figures.